Field of the Invention
The invention relates to a field-effect-controllable semiconductor component including a semiconductor body having an inner zone of a first conduction type which adjoins an upper surface of the semiconductor body, an anode zone of a second conduction type which adjoins a lower surface of the semiconductor body, at least one base zone of the second conduction type which is embedded in the upper surface of the semiconductor body, at least one emitter zone of the first conduction type which is embedded in the base zone, an emitter electrode which is disposed above the upper surface of the semiconductor body and is conductively connected to the emitter zone, a collector electrode which is disposed below the lower surface of the semiconductor body and is conductively connected to the anode zone, and a gate electrode which is disposed above the upper surface of the semiconductor body and covers parts of the base zone and of the emitter zone, with an insulating clearance.
A semiconductor component of the above-mentioned type has been disclosed in the form of an IGBT (Insulated Gate Bipolar Transistor) and thoroughly described in U.S. Pat. No. 4,364,073, for example. All known IGBTs are constructed essentially similarly, irrespective of the fabrication technology, and exhibit similar electrical behavior. In a forward mode, high reverse voltages can be blocked and large powers can be switched. In a reverse mode, the IGBTs exhibit a clear-cut diode characteristic on which a transistor characteristic (that can be influenced by the gate voltage) can be superposed. The load current path of an IGBT contains a diode in the forward direction. If the MOS transistor switches on, then a majority charge carrier current flows through the MOS channel through the base zone and through the pn junction to the collector zone. The consequence thereof is that minority charge carriers are injected into the inner zone. Some of the minority charge carriers flow directly through the base zone to the emitter electrode. That portion of the minority charge carrier current generates a voltage drop in the base zone.
Since the base zone acts as a sink for the minority carriers, in the planar IGBTs mentioned in the introduction it has not been possible to distinctly reduce the collector-emitter voltage in the forward case without reducing the breakdown voltage of the components. That is why IGBTs have been developed with trench structures derived from DRAM technology. The difference from the planar IGBTs mentioned in the introduction lies in the fact that a V-shaped or U-shaped trench is introduced into the inner zone by anisotropic etching. The gate electrode is disposed in the trench in such a way that it is insulated from the inner zone. On one hand, that results in very low sheet resistances and high packing densities.
On the other hand, however, that nonplanar configuration is disadvantageous because it greatly deviates from the relatively simple planar technology.